We report a 79-year-old woman, who had undergone surgery for papillary thyroid carcinoma 18 years previously and lung adenocarcinoma 15 years previously. She didn't receive any follow-up because she had no recurrence for 5 years in both diseases. She visited a local doctor with precordial pain and thorax discomfort as her chief complaints, where chest computed tomography indicated a 14 mm-sized nodule in the right lower lobe and 5-7 mm-sized small nodules in both lungs. Using endobronchial ultrasonography with a guide sheath (EBUS-GS) for the diagnosis in our department, the lesions were confirmed by ultrasonography, and a transbronchial biopsy was carried out under fluoroscopy. Pathologically, a sufficient amount of tumor cells were collected, and the findings of adenocarcinoma were obtained. Her condition was diagnosed as recurrent pulmonary metastases of thyroid papillary carcinoma because of the atypical columnar epithelial cells with nuclear variants and the papillary proliferation of intranuclear inclusion, and because of the positive findings in immunohistochemical staining for thyroglobulin. Since papillary thyroid carcinoma is positive for thyroid transcription factor-1 (TTF-1), which is widely used as a marker of lung adenocarcinoma, it cannot be used to differentiate between the two. It is often difficult to diagnose papillary thyroid carcinoma by bronchoscopy, because its progress is slow and the origin of the metastatic lung tumor is not in the bronchus, unlike primary lung cancer. However, a devised transbronchial biopsy procedure for slowly progressive metastatic lung tumors such as papillary thyroid carcinoma is considered to be a useful technique for diagnosis.
Keywords: bronchoscopy; endobronchial ultrasonography with a guide sheath; lung cancer; metastatic lung tumor; papillary thyroid carcinoma.